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DMA module
128
NS7520 Hardware Reference, Rev. D 03/2006
DMA module
Each DMA controller has a state machine and a block of static RAM referred to as
context RAM.
The context RAM contains the current state of each DMA channel.
The single state machine supports all DMA channels in parallel, by context
switching from channel to channel.
Figure 15: DMA controller block diagram
The DMA controller arbiter determines which channel the state machine currently is
operating.
Fly-by operation transfers
There are two modes of fly-by operation:
Read mode. Transfers data from memory to a peripheral device.
Write mode. Transfers data from a peripheral device to memory.
When configured for fly-by operation, the DMA controller transfers data between one
of the NS7520 internal peripherals and a memory location. The DMA controller does
DMA channel
arbiter
DMA control
state machine
BBus
Data
out
Data
in
DMA
context RAM
128 x 32
Bus interface
Channel
transfer
attributes